- A
The rule order is incorrect; the allow rule is below the 'Deny All' rule.
Since the logs show the traffic matches the deny rule, the allow rule must be positioned lower in the rulebase.
- B
The application 'web-browsing' is not being properly identified by App-ID.
Why wrong: If App-ID failed, the traffic might not match the rule, but the log would show a different action or no match.
- C
The source address object for the allow rule is misconfigured with a wrong subnet mask.
Why wrong: While a misconfigured address object could cause a mismatch, the log indicates the traffic matched the deny rule, not that it failed to match the allow rule.
- D
The User-ID agent is overriding the allow rule and triggering a block action.
Why wrong: User-ID does not override rule actions; it only adds user context.
PCNSA Securing Traffic Practice Question
This PCNSA practice question tests your understanding of securing traffic. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A network administrator is troubleshooting a connectivity issue. The firewall has a security rule that allows traffic from the Trust zone to the Untrust zone for the subnet 192.168.1.0/24 with application 'web-browsing'. However, users in that subnet cannot access any external websites. The administrator checks the logs and sees that the traffic is being blocked by a rule named 'Deny All' that is listed before the allow rule in the policy order. What is the most likely cause of the problem? The rule order is incorrect; the allow rule is below the 'Deny All' rule. The source address object for the allow rule is misconfigured with a wrong subnet mask. The application 'web-browsing' is not being properly identified by App-ID. The User-ID agent is overriding the allow rule and triggering a block action.
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The rule order is incorrect; the allow rule is below the 'Deny All' rule.
Option A is correct because in Palo Alto Networks firewalls, rules are evaluated in top-down order. If the 'Deny All' rule is above the allow rule, it will match first and block traffic. Options B, C, and D are plausible but less likely given the log evidence.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The rule order is incorrect; the allow rule is below the 'Deny All' rule.
Why this is correct
Since the logs show the traffic matches the deny rule, the allow rule must be positioned lower in the rulebase.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
CIDR notation defines the prefix length.
- ✗
The application 'web-browsing' is not being properly identified by App-ID.
Why it's wrong here
If App-ID failed, the traffic might not match the rule, but the log would show a different action or no match.
- ✗
The source address object for the allow rule is misconfigured with a wrong subnet mask.
Why it's wrong here
While a misconfigured address object could cause a mismatch, the log indicates the traffic matched the deny rule, not that it failed to match the allow rule.
- ✗
The User-ID agent is overriding the allow rule and triggering a block action.
Why it's wrong here
User-ID does not override rule actions; it only adds user context.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Trap categories for this question
Command / output trap
If App-ID failed, the traffic might not match the rule, but the log would show a different action or no match.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
- CIDR notation defines the prefix length.
- Block size helps identify subnet boundaries.
- Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
- The required host count determines the smallest suitable subnet.
TExam Day Tips
- Write the block size before choosing the subnet.
- Check whether the question asks for hosts, subnets or a specific address range.
- Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related PCNSA subnetting questions on CIDR, address ranges, and subnet selection.
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Securing Traffic — study guide chapter
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Securing Traffic practice questions
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FAQ
Questions learners often ask
What does this PCNSA question test?
Securing Traffic — This question tests Securing Traffic — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The rule order is incorrect; the allow rule is below the 'Deny All' rule. — Option A is correct because in Palo Alto Networks firewalls, rules are evaluated in top-down order. If the 'Deny All' rule is above the allow rule, it will match first and block traffic. Options B, C, and D are plausible but less likely given the log evidence.
What should I do if I get this PCNSA question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related PCNSA subnetting questions on CIDR, address ranges, and subnet selection.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
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Last reviewed: Jun 24, 2026
This PCNSA practice question is part of Courseiva's free Palo Alto Networks certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCNSA exam.
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